The Biostatistics, Epidemiology and Data Management Core has two major responsibilities: 1) the entry and management of the ADRC data; and 2) providing statistical epidemiological expertise to the design, conduct and analysis of studies involving these data, alone or in combination with other data. The entry and management of the ADRC data are performed by the Data Unit. Data are entered using a full double-entry system, and maintained on a series of IBM-compatible computers connected by a Local Area Network and using the data management package DBase III. Several other data sets are also maintained for the purpose of comparison with the ADRC data and, as appropriate, to be combined with these data. Statistical analyses are performed on IBM-compatible 80486 machines using a variety of software packages such as MBDP and SPSS, with smaller packages used for specific analyses as well as power and sample size calculations. The Core also functions as a conduit for researchers to request and obtain support in data management and analysis for their studies. Finally, an important function of the Core is to provide a forum for members and other interested parties to exchange information on methodologies and new developments, and to collaborate in performing research into improved methods of data collection and analysis. These improved methods will be especially important as we search for factors which affect the course of AD, and for treatment that may alter that course.